Helical cutter for synthetic fiber and honing device therefor



Nov. 22, 1966 J. A. HANCOCK ETAL 3, 6, 9

HELICAL CUTTER FOR SYNTHETIC FIBER AND HONING DEVICE THEREFOR Filed May 18, 1965 4 Sheets-Sheet 1 FIG.1

D J L D 3' u 9 INVENTORS "1F, JACK ARNET HANCOCK JAMES EARL SPELLMAN ATTORNEY Nov. 22, 1966 J. A. HANCOCK ETAL 3,286,569

HELICAL CUTTER FOR SYNTHETIC FIBER AND HONING DEVICE THEREFOR Filed May 18, 1965 4 Sheets-Sheet 2 INVENTORS JACK ARNET HANCOCK Z22 JAMES EARL SPELLMAN BY- wzz ATTORNEY Nov. 22, 1966 J. A. HANCOCK ETAL 3, 6,5 9

HELICAL CUTTER FOR SYNTHETIC FIBER AND HONING DEVICE THEREFOR Filed May 18, 1965 4 Sheets-Sheet 5 FIG-3 INVENTORS JACK ARNET HANCOCK JAMES EARL SPELLMAN BY MA ATTORNEY Nov. 22, 1966 .1. A. HANCOCK ETAL 3,286,569

HELICAL CUTTER FOR SYNTHETIC FIBER AND HONING DEVICE THEREFOR Filed May 18, 1965 4 Sheets-Sheet 4 INVENTORS JACK ARNET HANCOCK JAMES EARL SPELLMAN BY 9M4 a e i ATTORNEY United States Patent 3,286,569 HELICAL CUTTER FOR SYNTHETIC FIBER AND HONING DEVICE THEREFOR Jack Arnet Hancock, Nashville, Tenn, and James Earl Spellman, Unionville, Pa, assignors to E. I. du Pont de Nernours and Company, Wilmington, Del., a corporation of Delaware Filed May 18, 1965, Ser. No. 458,835 Claims. (Cl. 83-174) This invention is a continuation-in-part of Serial No. 281,234, filed May 17, 1963, and now abandoned.

This invention relates to apparatus for cutting moving bundles of tow of substantially continuous synthetic filaments into staple fiber of controlled lengths.

Synthetic fibers are produced in continuous lengths. Adaptation for processing on the staple textile equipment used to convert fibers to useful articles requires that these continuous fibers be cut to lengths approximating those of the natural fibers for which the textile equipment was designed. One of the more successful of the means for cutting bundles of tow to staple length fibers is the helical knife cutter, such as described in U.S. Patent No. 2,694,447.

The helical knife cutter, however, requires periodic sharpening. Unless the blades are restored to their original sharpness at periodic intervals, typically after cutting only 2000l0,000 pounds of tow depending upon the fiber involved, the extra mechanical heat developed in the passage of the dull blade through the fiber bundle tends to fuse neighboring filaments together at their ends. Staple containing such fused filaments does not process satisfactorily on textile processing equipment.

Due to the mechanical complexity of the helical knife cutter, maintenance of blades in an adequately sharp condition requires substantial down time of production machinery even though considerable investment is entailed in provision of standby cutting apparatus. Also, the extreme precision required to achieve an adequately sharpened blade requires the time of a highly skilled specialist to perform the sharpening.

An object of this invention is to provide a process and means for efficient cutting of synthetic tow with minimum fusing of the cut staple ends.

A further object is to provide a helical knife cutter which will produce uniformly satisfactory staple fibers throughout the life of the knife with minimum machine down time for knife-sharpening.

A still further object is to provide means for essentially continuous honing of a helical cutter while the cutter is in operation.

These and other objects are attained in this invention by means of a novel, continuous, rotary hone in combination with an especially designed helical blade fabricated from a member of the class of materials adapted to continuous honing on one edge only, said hone being cupshaped, the open end of said cup being the working portion, said hone being mounted on the helical knife cutter frame in such a manner as properly to contact the knife along its entire working edge during selected revolutions thereof, whereby to restore the original sharpness as required throughout the life of the blade, there being means to permit advancement toward the blade, as required, to maintain the honing device in an operative alignment to ice restore original sharpness and to compensate for wear of both blade and hone.

This invention will be understood by reference to the following detailed description and drawings, which illustrate a preferred embodiment.

In these drawings,

FIGURE 1 is a plan view of the helical knife cutter illustrating the approximate positioning of the continuous hone.

FIGURE 2 is an elevational view of the cutter, looking from the top of FIGURE 1 downwards, and illustrating the positioning of the helical knife relative to the tow to be cut.

FIGURE 3 is an enlarged plan detail, partly in perspective, of the hone mounted on the cutter.

FIGURE 4 is an elevational View, partly in section, of the hone and cutter assembly.

FIGURE 5 shows a typical blade lay-out, when viewed from the front of FIGURE 2.

FIGURE 6 is a top view on FIGURE 5 and shows a detail of the bevelled cutting edge, while FIGURE 7 is a diagram showing how the angle on of FIGURE 6 is related to the basic dimensions of the knife blade shown in FIGURE 5,

The general operation of the cutter will be understood by reference to FIGURES 1 and 2. Motor 10 simultaneously drives both conveyor belt shaft 11 and cut-tel shaft 12 by suitable pulleys and gears as indicated. As conveyor belt shaft 11 rotates, it drives continuous link belts 13 and 14 through sprocket wheels 18 and 19 mounted thereon. Identical sprocket wheels are mounted on idler shaft 15. The link belts support clamping members 16, only two of which are shown for purposes of clarity, which holds the tow. Within each clamping member is a powerful spring means which closes jaws 17 on the bundle of tow within the clamping member opening as permitted by movement of cam follower 20 along cam 21. By these means, tow 9 is tightly clamped while passing beneath knife 22, which rotates between clamps to sever the bundle. A more detailed description of the general operation of this type cutter can be found in the aforementioned patent.

A preferred embodiment of this invention is illustrated in FIGURES 3 and 4 and in the description which follows. The rotary hone installation of this embodiment is also indicated in FIGURE 1. With reference to FIG- URES 3 and 4, mounting 23 for electric motor 24, which serves as driver for the hone wheel, is installed on housing 25 of the outboard end of cutter shaft 12. This mounting provides good unity of hone and blade, avoiding problems that might arise due to independent vibration of individual components. The mounting incorporates a feed mechanism 26, which serves to adjust honing wheel 27 in precise relationship to knife 22. Adaptor plate 28 provides means (not detailed) for precisely establishing angularity in the horizontal plane of the axis of rotation of the hone relative to the axis of rotation of cutter shaft 12. Struts 29 illustrate suitable means for precisely adjusting vertical .angularity of the hones axis of rotation.

Precise positioning of the honing wheel by means of feed mechanism 26 is important, too. It has been found advantageous to incorporate a wheel pressure monitor circuit to provide an indication of the proximity of the honing wheel to the blade. The said circuit (enclosed in box 40, FIGURE 4, and connected by cable 41 to motor 24) consists of an electrical bridge circuit which indicates the change in motor load caused by contact of the honing wheel with the blade. It has been found that, even at the lowest sensitivity of the wheel pressure monitor, a significant increase in load occurs as initial contact is established. Adjustments in positioning can be accomplished manually, as indicated by the monitor, or can be made automatically by feeding the signal from the monitor to a suitable servomechanism, comprising for instance an amplifier and a transducer, such as a reciprocating ratchet or a reversible, motor-driven screw advance. (For further details, see Servomechanism Fundamentals, by H. Lauer, R. Lesnick and L. Matson; McGraw-Hill Book Co., 1947.)

Knife 22 (FIGURE 5) is a 90 segment of a circular cermet blade, preferably comprising tungsten carbide, titanium carbide or an equivalent. It is essential that the blade be capable of being honed from one side of the edge only without development of a wire along the opposite side (this excludes most materials normally used for cutlery which must be honed from both edges). The blade is rigidly fastened to rotor 30 substantially at rightangles to the axis of shaft 12 but in a skewed attitude with respect to said axis whereby to give the cutting edge a lead (axis-wise component) as required to follow the movement of the tow and to mesh with clamps 16 as they move the tow bundle in a horizontal, straight line. This lead may be adjusted to the requirement of each cut length as desired, but adjustment is generally not necessary for a moderate increase in cut length. The blade cuts the tow bundle once per revolution of shaft 12. The cut is a slicing action resulting from the curved rise from its leading edge 222 to its trailing edge 223 as clearly indicated in FIGURES 2 and 5. The slower advance of the blade through the tow as a result of this slicing action provides a substantial advantage over the rapid blade passage of the impact-type cutters. The slicing action results in reduced blade wear or dulling. Especially when the blade is kept sharp, the slicing action develops less heat during passage through the tow, which tends to minimize fused ends. Fused fibers give difficulties in textile processing.

Honing wheel 27 is a commercial cup-shaped honing wheel having a flat, circular, ring honing surface, whose outside diameter is 6 inches and width of ring is 1 inch. A diamond impregnated working surface is required to hone the tungsten carbide knife selected for this embodiment.

FIGURES 5 and 6 illustrate the 2 /2-inch blade rise employed in this particular embodiment and the preferred edge angles. It has been found that a cutting edge of about 19 to 31 provides the optimum balance between cutting etiiciency (favored by a small angle) and blade strength (favored by a large angle).

To insure contact between the honing surface and all points on the knife edge, it is necessary that the axis about which the honing surface revolves make an angle with the shaft of the cutter equal to the angle whose tangent is the ratio of the cutting edge lead to the cutting edge rise (FIGURE 7). The lead is the distance measured along the axis of the cutter between the leading point 222 of the cutting edge and its trailing point 223. The rise is the increase in length of radius between the two points (FIGURE 5).

For instance, where the staple prepared is to be 1 /2 inches long, and the knife blade is a 90 segment of a circle, the lead will have to be inch (i.e., of the length of the staple). In the preferred design under discussion, the rise in the knife blade is 2 /2 inches. Consequently, the angle between honing shaft and cutter shaft must be in the vicinity of an angle on whose tangent is 0.15 (the ratio of to 2 /2 The angle needed is therefore about 85 to 9 as can be seen from FIGURE 7 (also, in FIGURE 4, wherein the cutter axis is horizontal). Accordingly, the honing surface will likewise contact the cutting edge at an angle of about 9, and will produce 4 thereon a bevel of this magnitude (FIGURE 6). The angle of the second bevel is, therefore, by difference, an angle of about 10 to 22.

As knife 22 rotates, it generates a conical surface of revolution due to its skewed attitude (lead) on the rotor 30 and its rise from a 1 /2 inch projection (on a vertical plane) at its leading edge to a 4-inch projection at its trailing edge (FIGURE 5). To assure contact of the cutting edge with the hone along the entire cutting surface, it is necessary that honing wheel 27 be positioned in such a way that one side of honing annulus lies along a line which traverses the entire generated surface of revolution. The exact angle required will depend on the rise and lead of the knife. With the small lead entailed in a knife wherein the total rise is taken in of rotation, as is illustrated in this embodiment, the edge of the knife (when projected on a vertical plane) approximates a segment of a circle closely enough that final adjustment from a circular to the required elliptical shape can be accomplished by honing after grinding of the two blade bevels and installation on rotor 30.

Due to the specific geometry of this particular embodiment, it was found advantageous to cant the hone slightly (about 1.5 out of the vertical plane which embraces the axis of rotation of the cutter shaft 12 (FIGURE 3). By this means it was possible to achieve continuous contact (at effective honing speeds) with the blade during its entire passage using a commercially available honing wheel. In this case, the line of knife edge contact with the wheel moves around about a 90 segment of the wheel circumferentially with the blade rise.

It has been hereinbefore mentioned that a cup-shaped hone is employed in the apparatus of this invention. That the use of this type of bone is a necessary element of this invention will be apparent through a consideration of FIGURE 4, which shows the remote edge of the hone in contact with one side of the knife edge at the point where the knife is vertically cross-sectioned. By means of the cant hereinbefore described, the near edge of the hone (that not shown but oriented above the plane of the drawing) is not in contact with the blade. The entire working surface of the hone is used during each of its revolutions while it is in contact with the blade; therefore, there is no partial wear of this surface and development of an edge-damaging shoulder on the hone as would be the case if it were a flat disc or cylinder.

It will be obvious that, except for contact resulting from machine vibration, the first measurable wear at the juncture of blade 22 and hone 27 will be observed as a loss in honing contact. To maintain the hone in an operative alignment it is necessary to employ an advancing device such as that indicated as feed mechanism 26. The hone-advancing device may be adjustable by hand. However, in some cases, it is preferably to utilize the signal generated by the monitor 40 (FIGURE 4) to advance the hone automatically by transducer means (as hereinbefore described) as is required to maintain the optimum hone contact with the blade.

The foregoing description has emphasized apparatus wherein honing contact with the helical blade is made once during each revolution of the blade. It is apparent, however, that honing at this frequency is not essential to continuous operation of the cutter. It is within the scope of this invention, therefore, to schedule honing on some arbitrary basis such as, for example, for a short period following each five or ten minutes or several hours of continuous operation. Such honing may be initiated automatically or manually, as desired without interruption of the cutting operation.

Other variations which will achieve the minimum requirements of practical honing speed at all points along the line of contact and continuous contact along the working edge of the knife during each passage will be readily apparent to those skilled in the art.

The table below summarizes the pertinent specifications for the above-described specific embodiment, it being understood, however, that this invention is not limited to these details.

Cutter 90 segment of a helical knife,

as described above.

inch rim width, diamond impregnated; 600 grit.

Lead screw reduced by gearing to produce a 0.0005 inch Vertical inclination- Horizontal cant Hone advance feed per revolution of the screw. Rate of advance Variable, depending on to'w being cut; typically 0.0025 inch/ 1,000,000 cuts.

A comparison of cutter performance with continuous honing of the 90 blade and intermittent sharpening of both the 90 blade and the 360 segmented blade (when making 1% inches staple) shows that the continuous process (90 blade) maintains a zero fiber fusing level for over 1000 bales, i.e., for more than 22,000,000 cuts, whereas the intermittent process allows progressive deterioration to excessive fusing at 4-5 bales (110,000 cuts) for 90 blade and at 20-25 bales (500,000 cuts) for 360 blade. The continuously honed blade was essentially worn out before it was necessary to remove it from the line for replacement.

It will be understood that while we have described in some detail a tow cutting knife whose blade constitutes a 90 segment of a circle, the circular extent of the knife may be varied within reasonable limits, say within the range of 70 to 120 of a circle. It is, however, definitely preferred in this invention to have no more than one such blade on the cutting cylinder (in contrast with Hull, US. Patent No. 2,694,447, who uses a large plurality of 90 blades spaced successively on a cylinder to outline a helix of several turns). Otherwise, the installation of a plurality of honers with attendant monitoring and control devices which would be required, is apt to complicate the apparatus beyond economical practicability.

Other alternative embodiments which accomplish the objectives of this invention without departing from the spirit and scope thereof will be readily visualized by those skilled in the art. Accordingly, this invention is to be understood as not limited by the specific embodiment described, but only by the following claims.

What is claimed is:

1. In an apparatus for chopping a moving bundle of synthetic fiber tow into bundles of staple fiber, the combination of an essentially helical cutter having a radial rise supported upright on a cylinder which revolves on its own axis with a speed adjusted to harmonize with the linear motion of said tow whereby to cut across the entire bundle of tow at essentially the same distance from an immediately preceding cut, said helical cutter being fabricated from a material adapted to continous honing on one edge, a honing device adapted to make honing contact with the cutting edge of said helical cutter recurrently during the working period of the latter, said honing device being cup-shaped with the open end of the cup being the working portion, said honing device being mounted so as to properly contact said helical cutter along its entire working edge during selected revolutions thereof and means permitting advancement of said honing device toward said helical cutter whereby to maintain said honing device in an operative alignment.

2. The apparatus of claim 1 wherein said cup-shaped honing device comprises a flat ring formed by the space between two concentric circles, the diameter of the outer circle being of a length not less than twice the radial rise in said helical cutter from its leading point to its trailing point.

3. The apparatus of claim 2 wherein said flat ring is mounted for rotation on an axis passing through the center of the ring and at right angles to its plane, said center being fixed in space at a point outside of the surface of revolution formed by the rotation of said helical cutter.

4. The apparatus of claim 1 wherein said material is tungsten carbide.

5. The apparatus of claim 1 wherein said material is titanium carbide.

References Cited by the Examiner UNITED STATES PATENTS 1,928,481 9/ 1933 Cole 51247 2,062,990 12/1936 Forbes 83l74 2,297,468 9/ 1942 Graupner 51247 2,694,447 11/ 1954 Hull 83-340 2,726,412 12/1955 Ruhr 83174 2,738,628 3/ 1956 Lust 146--94.1 2,815,619 12/1957 Brownley 51-247 WILLIAM S. LAWSON, Primary Examiner. 

1. IN AN APPARATUS FOR CHOPPING A MOVING BUNDLE OF SYNTHETIC FIBER TOW INTO BUNDLES OF STAPLE FIBER, THE COMBINATION OF AN ESSENTIALLY HELICAL CUTTER HAVING A RADIAL RISE SUPPORTED UPRIGHT ON A CYLINDER WHICH REVOLVES ON ITS OWN AXIS WITH A SPEED ADJUSTED TO HARMONIZE WITH THE LINEAR MOTION OF SAID TOW WHEREBY TO CUT ACROSS THE ENTIRE BUNDLE OF TOW AT ESSENTIALLY THE SAME DISTANCE FROM AN IMMEDIATELY PRECEDING CUT, SAID HELICAL CUTTER BEING FABRICATED FROM A MATERIAL ADAPTED TO CONTINUOUS HONING ON ONE EDGE, A HONING DEVICE ADAPTED TO CONTINUOUS HONING CONTACT WITH THE CUTTING EDGE OF SAID HELICAL CUTTER RECURRENTLY DURING THE WORKING PERIOF OF THE LATTER, SAID HONING DEVICE BEING CUP-SHAPED WITH THE OPEN END OF THE CUP BEING THE WORKING PORTION, SAID HONING DEVICE BEING MOUNTED SO AS TO PROPERLY CONTACT SAID HELICAL CUTTER ALONG ITS ENTIRE WORKING EDGE DURING SELECTED REVOLUTIONS THEREOF AND MEANS PERMITTING ADVANCEMENT OF SAID HONING DEVICE TOWARD SAID HELICAL CUTTER WHEREBY TO MAINTAIN SAID HONING DEVICE IN AN OPERATIVE ALIGNMENT. 